"Phil Kangas" wrote:


"Wes" wrote in message
BillMe wrote:
[snip]

Serial tap. A series of taps that work you up to an
agressive thread form.

Wes

This looks like a good place to add my attempt at making
such a tap.
There is a problem with fire hydrant gate valves. What
happens is that
when the valve is closed there is only a very short thread
engagement
between the gate and the actuating screw and after some wear
the
threads lose engagement and the valve cannot be opened. Not
good!
So I came up with a repair that involves a longer threaded
portion on the
gate. I've repaired several of them now with this tap. I
have posted a
pic to the dropbox, the text file has not appeared yet for
some reason
so I'll include it he

http://www.metalworking.com/DropBox/...ead_tap_01.jpg

This tap is a 1/2-4 double helix left hand thread used to
cut a thread to repair fire hydrant gate valves. It has
been used several times to cut threads in aluminum. Six
previous attempts were failures due to the wrong heat
treatment procedure. The last few threads are the only
ones that cut the final profile. The thread profile of
the actuating screw is definately a square thread. The
tap is made from W-1 drill rod and was done on a 9"
South Bend Model A workshop lathe. The flutes were cut
on a milling machine. Tap drill size is 25/64.


Nice bit of work. I searched the drop box, I can't find your .txt file. I hope our
benefactor keeps it in the box.

Obviously you have a taper attachent. Wish I did.

Wes